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Finding the Third Proportional to 489 and 780

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Solution

The third proportional to 489 and 780 is: 1,244.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    489 : 780 = 780 : x
  2. Step 2: Convert to fraction form
    489/780 = 780/x
  3. Step 3: Cross multiply
    489x = 780 × 780
  4. Step 4: Simplify right side
    489x = 608,400
  5. Step 5: Solve for x
    x = 608,400/489
  6. Step 6: Final answer
    x = 1,244.17

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Why These Related Problems?

These problems maintain the same ratio (1.60) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.